[clang] [ARM] Empty structs are 1-byte for C++ ABI (PR #124762)

[Oliver Stannard via cfe-commits]

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@@ -588,7 +615,8 @@ ABIArgInfo ARMABIInfo::classifyReturnType(QualType RetTy, bool isVariadic,
 
   // Otherwise this is an AAPCS variant.
 
-  if (isEmptyRecord(getContext(), RetTy, true))
+  if (isEmptyRecord(getContext(), RetTy, true) ||
+      getContext().getTypeSize(RetTy) == 0)
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ostannard wrote:

This is needed for the `SortOfEmpty` case, which isn't considered empty, but does have size 0.

https://github.com/llvm/llvm-project/pull/124762